In wireless networks like LTE, a User Equipment, UE, obtains access to a network as a result from the cooperation of several network nodes. Such an access means that a certain amount of resources will be used in the network nodes by the UE for the duration of the intended service. Granting service of too many UEs would mean that network nodes exhaust their resources to the point that none of the connected UEs can be served at a satisfactory level.
At some point it may therefore be necessary to reject service requests from UEs seeking access to the network. The functionality to determine whether to grant or reject a request for service is often referred to as Admission Control.
For base stations, such as eNBs in LTE networks, there are two aspects of prioritization to consider at congestion: (i) packet-level prioritization as represented by Quality of Service Identifier, QCI; and (ii) bearer-level prioritization executed at bearer-level establishment/modification and pre-emption, as represented by Allocation and Retention Priority, ARP. Admission control at bearer level provides a higher level of accessibility for bearers, such as Evolved Packet System, EPS, bearers, associated with more prioritized ARP.
FIG. 1a schematically illustrates nodes in an LTE-type communication network. A UE 101 is located in a cell 103 served by an eNB 102. The eNB is connected to a Mobility Management Entity, MME 104. The MME is connected to a Serving GateWay, SGW or S-GW, which is connected to a Packet Data Network GateWay PGW or P-GW.
FIG. 1b illustrates the concept of bearers in LTE-type communication systems. To achieve an End-to-End service, e.g. transfer of data, between a wireless terminal and a peer entity, a number of different so-called bearers are involved. EPS bearers, which have already been mentioned, extend from a wireless terminal, a UE, to a Packet Data Network Gateway, P-GW. EPS bearers are composed of Evolved-Radio Access Bearers, E-RABs, and S5/S8 bearers, where “S5/S8” refers to an interface between the S-GW and P-GW. An E-RAB, in its turn, is composed of a radio bearer and an S1 bearer, where S1 denotes an interface. Herein, the focus is on allocation of radio resources and the set-up of E-RABs for EPS bearers. When referring to radio resources and bearers herein, the terms “E-RAB” and “radio bearer” may be used interchangeably, even though it is not exactly the same thing, as can be seen e.g. in FIG. 1b. The MME is not shown in FIG. 1b, but is, in an LTE network, typically located between eNB and S-GW. From the P-GW to a Peer entity, data associated with a service is sent over an external bearer.
Before starting a service, the bearers necessary to carry out the service need to be set up. The setup of these bearers is accomplished in a so-called Service Request procedure. A Service Request procedure can be initiated either by a UE or by the network, which will be further described below.
UE Initiated Service Request
For LTE, the procedure for a UE triggered service request is done in several steps, which will be described below with reference to FIG. 2, and, in more detail, further below:                The UE performs an RRC connection establishment procedure, if in state Idle (not shown in FIG. 2).        The UE sends a Non-Access Stratum, NAS, message “(Extended) Service Request” to the MME, indicated as message “1.” and “2.” in FIG. 2.        The MME requests eNB to establish the E-RABs for the EPS bearers by means of an Initial Context Setup message, indicated as message “4.” in FIG. 2.Network Initiated Service Request        
For LTE, a network-initiated service request procedure involves UE, eNB, MME and the SGW. The procedure is performed in several steps, which will be described below with reference to FIG. 3 and in more detail further below:                A Downlink Data Notification message is sent from the SGW to the MME advertising there is data on some EPS Bearers. The Data notification message is indicated as “2a.” in FIG. 3.        The MME pages the UE, indicated as messages “3a” and “4a” in FIG. 3.        The UE responds to the paging and performs the steps indicated for UE triggered Service Request, i.e. the procedure described above with reference to FIG. 2. The box indicated with “5” in FIG. 3 thus represents a service request procedure as the one illustrated in FIG. 2.        
In the Initial Context Setup message, “5.” in FIG. 2, the MME indicates ARP for each E-RAB. The ARP information may then be used by the eNB to perform admission control, e.g. deciding whether or not to allocate radio resources for the requested service for the UE in question. However, the inventors have realized that there are problems associated with achieving an adequate admission control on bearer level, and thus with achieving adequate handling of radio resources, which will be further described below.